HTC M9 is expected to have the android 6.0 update, all users of this device are encourage to watch out for notifications concerning the update.
The HTC One M9 is currently running on Android version 5 (Lollipop) and is will receive 2 updates; a computer code update and an Android 6.0 update.
The first update is larger than the second; 1.21 GB, with the computer code version 3.35.617.12.
The second which is quite smaller is 99.47 update with the version 2.11.617.180.
Many enhancement like Android 6.0 candy options and battery saver option. The HTC M9 will feature new options that will support higher app permission.
When you get the notification for the OTA update, ensure that you have a good battery percentage on your device and you are connected to a WLAN network
If you are currently enjoying the carrier version of the HTC M9, just be patient and wait for the android 6.0 update. As of now, the update is gradually entering the US.